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SHEET TWF·T-03 REV 2026-08-20 METHOD M.2026-08-20.1

Gas cylinder duration

Turns a marked free-gas volume or an idealised cylinder estimate, entered flow and arc-on duty into gas-on and elapsed planning minutes — the cylinder supplier’s data outranks every figure here.

Classification Planning estimate

InputsT-03
F-01 Input mode

Use the marked free-gas volume when the cylinder states one; otherwise the idealised estimate.

F-02
L

Marked or entered free-gas volume, greater than 0.

F-06
L/min

The flow set at the regulator or flowmeter, greater than 0.

F-07

Fraction of elapsed time with gas flowing — over 0 and at most 1; 0.5 means half the time.

JavaScript is off in this browser, so no live record can be issued. The worked example below walks the full method with real figures, and the blank card on this page prints as a worksheet.

R-GAS-nnn

Gas cylinder duration

Awaiting inputs — enter values and issue a record. Empty slots below print as a blank worksheet.

Field slots

F-01Input mode
F-02Available free gas
F-06Flow rate
F-07Arc-on duty fraction
RECORD VOID — inputs changed since issue. Recalculate to issue a new record.

Worksheet · https://theweldfab.com/tools/welding-gas-cylinder-duration-calculator/ · METHOD M.2026-08-20.1 · REV 2026-08-20

Worked example

STATIC — not a live result

An idealised 50 L water-capacity cylinder from 200 bar down to a 20 bar reserve gives ≈ 9,000 L of usable free gas; at 15 L/min that is 600 gas-on minutes, and at a 0.5 arc-on duty fraction ≈ 1,200 elapsed minutes — 20 hours.

R-GAS-EX

Gas cylinder duration

Planning estimate

≈ 1 200 min elapsed at the entered duty

Entered assumptions

F-01Input modeIdealised cylinder estimate
F-03Water capacity50 L
F-04Starting pressure200 bar
F-05Reserve pressure20 bar
F-06Flow rate15 L/min
F-07Arc-on duty fraction0.5

Planning figures

R-01Idealised usable free gas9 000 L
R-02Gas-on time600 min
R-03Elapsed time at entered duty1 200 min
R-04Elapsed time20 h

Planning support only — verify against nameplate/manufacturer data.

RECORD VOID — inputs changed since issue. Recalculate to issue a new record.

Method

M.2026-08-20.1

Mode A takes the marked or entered free-gas volume directly. Mode B idealises the cylinder: usable free gas L ≈ water capacity L × (start bar − reserve bar). Both modes then share two lines:

  • gas-on minutes = usable free gas ÷ flow L/min
  • elapsed minutes = gas-on minutes ÷ arc-on duty fraction

Worked figures: 50 L × (200 − 20) bar = 9,000 L of idealised usable gas; at 15 L/min, 600 gas-on minutes; at a 0.5 arc-on duty fraction, 1,200 elapsed minutes — 20 hours.

Limits & stop conditions

T-03
  • Ideal-gas planning approximation: regulator behaviour, temperature, residual gas, leaks and the flow actually delivered at the torch all change real duration.
  • HOLD — reserve pressure at or above the starting pressure, a duty fraction outside 0 to 1, or any missing or non-finite entry keeps the record unissued.
  • The cylinder supplier’s data outranks this estimate.

Source register

  1. S1 Metal Inert Gas (MIG) Welding — Process and Applications (Job Knowledge 4) ↗ TWI Ltd retrieved 2026-08-19
Bench Awaiting values